The present invention relates in general to thermal processing systems, and, more particularly, to a method for processing semiconductor devices using rapid thermal processing systems.
Rapid Thermal Processing (RTP) was started as a research technique over 25 years ago using pulsed laser beams. As the semiconductor industry is moving towards submicron devices, RTP is becoming a core technology step in the development and mass production of ultra-large system integration (ULSI) devices. RTP processors attain a desired processing temperature rapidly, without the need for a lengthy xe2x80x9cramp upxe2x80x9d period. This quick ramp up minimizes the thermal budget and the total time of the process thereby allowing more dense designs and fewer failures from internal crystalline dislocations. Thus, RTP processors allow microelectronic devices to be fabricated at high temperatures without causing dopant diffusion or other unwanted side effects. Since RTP processors typically process semiconductor wafers, the term xe2x80x9cwaferxe2x80x9d will be used herein to designate any device, material or substrate processed in the RTP processor.
In contrast.with a conventional furnace which typically uses resistive heating units, an RTP processor typically uses radiant heat sources, for example, arc lamps or tungsten-halogen lamps. A small processing chamber is typically used, to provide a controlled environment for the wafer to be processed and to efficiently couple the heat energy from the radiant energy source to the wafer. RTP has been utilized in a number of different semiconductor processing steps including nitridation, oxidation, dopant activation, silicide formation, and ion implantation damage removal. RTP processors have also been used in rapid thermal chemical vapor deposition (RTCVD) processes.
Two major design considerations in RTP are temperature control and production time. Efficient coupling of the radiant heat from the lamps to the wafer is necessary so that large increases in wafer temperature can be produced in a short time. Moreover, in producing the rapid increase in wafer temperature, a uniform temperature distribution must be provided across the wafer. Lack of uniformity can produce excessive microelectronic device variation across the wafer or may render the wafer unuseable because of internal crystalline dislocation or even wafer cracking. The temperature across the wafer is also difficult to control, especially during the ramp up stage when the lamps are activated. Further, production time is increased as the RTP processor must ramp up to the desired temperature and ramp down once the process step is complete. This time for ramping up and ramping down, while still much less than with prior art furnaces, increases production time and reduces the throughput of the process.
Accordingly, there is a need for a method of processing semiconductor devices in which the processing temperature may be easily and readily controlled. There is a further need for such a method which may be used in a variety of temperature and pressure environments. Preferably, such a method would decrease production time and increase the throughput of the process. Preferably, such a method would be relatively inexpensive and easy to perform.
The present invention meets this need by providing a method in which a predetermined amount of power is applied to the radiant heat sources in an RTP chamber prior to inserting the wafer to be processed into the chamber. The predetermined amount of power is set so that the wafer reaches the desired processing temperature quickly without the typical ramp up time. The predetermined amount of power remains constant before, during, and after processing such that there is also no ramp down of power associated with the process. The production time of the process is thus reduced. A reflective plate may be positioned within the chamber so that the radiated properties of the wafer are substantially independent of the emissivity of the wafer thereby minimizing wafer to wafer variation. Emissivity variation may also be minimized by positioning the wafer near a plate within the chamber so as to form an isothermal cavity between the wafer and the plate.
According to a first aspect of the present invention, a method of manufacturing semiconductor wafers in a processing chamber having at least one radiant heat source is provided. A predetermined amount of power is provided to the radiant heat source and a wafer is then positioned within the processing chamber. The predetermined amount of power applied to the radiant heat source is set so that the wafer reaches a predetermined temperature in a predetermined amount of time for carrying out a desired process in the processing chamber.
The radiant heat source may comprise a tungsten-halogen lamp. The pressure within the processing chamber during the desired process is greater than approximately 1xc3x9710xe2x88x9210 torr, and preferably, less than approximately 100 mtorr. The pressure within the processing chamber may be less than approximately 15,200 torr. The predetermined amount of time is less than approximately 10 seconds. Preferably, the predetermined amount of power remains substantially constant during the desired process.
According to another aspect of the present invention, a method of manufacturing semiconductor wafers in a processing chamber having at least one radiant heat source and at least one reflective plate is provided. A predetermined amount of power is applied to the radiant heat source and a first wafer having a first emissivity is positioned within the processing chamber such that the radiated properties of the first wafer are substantially independent of the first emissivity. The predetermined amount of power applied to the radiant heat source is set such that the first wafer reaches a predetermined temperature in a predetermined amount of time for carrying out a desired process in the processing chamber.
The method may comprise the step of positioning a second wafer having a second emissivity different from the first emissivity within said processing chamber such that the radiated properties of the second wafer are substantially independent of the second emissivity. An effective emissivity of the first wafer is approximately the same as an effective emissivity of the second wafer. Preferably, the reflective plate has an emissivity greater than approximately 0.6. A distance between the first wafer and the reflective plate is less than approximately 10 cm, and preferably, less than approximately 1 cm. Preferably, the pressure within the processing chamber is less than approximately 100 mtorr. The predetermined amount of power preferably remains substantially constant during the desired process.
According to yet another aspect of the present invention, a method of manufacturing semiconductor wafers in a processing chamber having at least one radiant heat source and at least one plate is provided. A predetermined amount of power is applied to the radiant heat source and a wafer is then positioned within the processing chamber such that an isothermal cavity is formed between the wafer and the plate. The predetermined amount of power applied to the radiant heat source is set so that the wafer reaches a predetermined temperature in a predetermined amount of time for carrying out a desired process in the processing chamber.
Preferably, a distance between the plate and the wafer is approximately 1-10 mm. Preferably, the plate comprises material selected from the group consisting of graphite, silicon, silicon carbide and carbon. The pressure within the processing chamber is preferably greater than approximately 1 mtorr. Preferably, the predetermined amount of power remains substantially constant during the desired process.
According to a further aspect of the present invention, a method of manufacturing semiconductor wafers in a cluster system having at least a first processing chamber and at least a second processing chamber is provided. Each of the first and second processing chambers include at least one radiant heat source positioned therein. The cluster system is maintained in a controlled ambient environment. The method comprises applying a first predetermined amount of power to the radiant heat source in the first processing chamber, applying a second predetermined amount of power to the radiant heat source in the second processing chamber, positioning a first wafer having a first emissivity within the first processing chamber so as to perform a first process, and positioning the first wafer within the second processing chamber so as to perform a second process. The first predetermined amount of power applied to the radiant heat source in the first processing chamber is set such that the first wafer reaches a first predetermined temperature in a first predetermined amount of time for carrying out the first process and the second predetermined amount of power applied to the radiant heat source in the second processing chamber is set such that the first wafer reaches a second predetermined temperature in a second predetermined amount of time for carrying the second process.
The first processing chamber may be different from the second processing chamber. The process may further comprise the step of transporting the first wafer from the first processing chamber to the second processing chamber in the controlled ambient environment. Preferably, the controlled ambient environment is substantially free of oxygen. The controlled ambient environment may be a vacuum or an N2 purged ambient maintained around the wafer during the transporting step. At least one of the first and second processing chambers may include at least one reflective plate positioned so that the radiated properties of the first wafer are substantially independent of the first emissivity. The method may further comprise the step of positioning a second wafer having a second emissivity different from the first emissivity within the one of the first and second chambers so that the radiated properties of the second wafer are substantially independent of the second emissivity. The effective emissivity of the second wafer is approximately the same as the effective emissivity of the first wafer. Preferably, the second wafer is positioned within the respective chamber after the first or second process is performed on the first wafer. At least one of the first and second processing chambers may include at least one plate positioned so as to form an isothermal cavity between the wafer and the plate. Preferably, the first and second predetermined amounts of power remain substantially constant during the first and second processes, respectively.
According to a still further aspect of the present invention, a method of forming hemispherical grained silicon (HSG) is provided. A layer of starting material is formed on a wafer in a first process. The layer of starting material is seeded with a seed material in a second process. The wafer is annealed in a third process. At least one of the second and third processes is carried out in a processing chamber having at least one radiant heat source positioned therein. A predetermined amount of power is applied to the processing chamber prior to positioning the wafer in the processing chamber so that the wafer reaches a predetermined temperature in a predetermined amount of time for carrying out the respective process.
Preferably, the second process is carried out in the processing chamber at a predetermined temperature of approximately 100 to 1000xc2x0 C., a pressure less than approximately 10 torr, and a gas flow rate approximately 1 sccm to 10 slm. Preferably, the third process is carried out in the processing chamber at a predetermined temperature of approximately 200 to 1500xc2x0 C., and a pressure less than approximately 760 torr. Preferably, the predetermined amount of power remains substantially constant during the respective process. Preferably, at least the second and third processes are carried out in a controlled ambient environment so that as the wafer is maintained in the controlled ambient environment between processes.
The other of the second and third processes is preferably carried out in a second processing chamber having at least one radiant heat source positioned therein. A second predetermined amount of power is applied to the second processing chamber prior to positioning the wafer in the second processing chamber so that the wafer reaches a second predetermined temperature in a second predetermined amount of time for carrying out the respective process. Preferably, the processing chamber is different from the second processing chamber. The method may further comprise the step of transporting the wafer from the processing chamber to the second processing chamber in a controlled ambient environment. Preferably, the another predetermined amount of power remains substantially constant during the respective process.
The method may further comprise the step of cleaning the wafer prior to performing at least one of the second and third processes. The step of cleaning the wafer prior to performing at least one of the second and third processes may be carried out in the processing chamber or another processing chamber at a predetermined temperature of approximately 10 to 200xc2x0 C. The method may further comprise a plurality of the processing chambers for carrying out each of the first, second and third processes. Preferably, the plurality of chambers are maintained in a controlled ambient environment. The method may further comprise the step of forming a dielectric layer above the annealed layer.
According to yet another aspect of the present invention, a method of forming HSG is provided in which a layer of starting material is formed on a first wafer in a first process. The layer of starting material is seeded with a seed material in a second process and the first wafer is annealed in a third process. At least one of the second and third processes is carried out in a processing chamber having at least one radiant heat source and at least one reflective plate positioned therein. The first wafer has a first emissivity such that when the first wafer is positioned in the processing chamber the radiated properties of the first wafer are substantially independent of the first emissivity. A predetermined amount of power is applied to the processing chamber prior to positioning the first wafer in the processing chamber so that the first wafer reaches a predetermined temperature in a predetermined amount of time for carrying out the respective process.
According to a further aspect of the present invention, a method of forming HSG is provided in which a layer of starting material is formed on a wafer in a first process. The layer of starting material is seeded with a seed material in a second process and the wafer is annealed in a third process. At least one of the second and third processes is carried out in a processing chamber having at least one radiant heat source and at least one plate positioned therein. The wafer is positioned in the processing chamber such that an isothermal cavity is formed between the wafer and the plate. A predetermined amount of power is applied to the processing chamber prior to positioning the wafer in the processing chamber so that the wafer reaches a predetermined temperature in a predetermined amount of time for carrying out the respective process.
According to a still further aspect of the present invention, a method of forming HSG is provided in which a layer of starting material is formed on a first wafer having a first emissivity in a first process. The layer of starting material is seeded with a seed material in a second process. The second process is carried out in a first processing chamber having at least a first radiant heat source positioned therein with a first predetermined amount of power being applied to the first radiant heat source prior to positioning the first wafer in the first processing chamber so that the first wafer reaches a first predetermined temperature in a first predetermined amount of time for carrying out the second process. The first wafer is annealed in a third process. The third process is carried out in a second processing chamber having at least a second radiant heat source positioned therein with a second predetermined amount of power being applied to the second radiant source prior to positioning the first wafer in the second processing chamber so that the first wafer reaches a second predetermined temperature in a second predetermined amount of time for carrying out the third process. The first wafer is transported from the first processing chamber to the second processing chamber in a controlled ambient environment.
Preferably, the first and second processing chambers form part of a cluster system. The method may further comprise the step of cleaning the first wafer prior to performing one of the second and third processes. The step of cleaning the first wafer prior to performing one of the second and third processes is carried out in a cleaning chamber with the cleaning chamber forming part of the cluster system.
According to another aspect of the present invention, a method of forming HSG is provided in which a layer of starting material is formed on a wafer in a first process. The layer of starting material is seeded with a seed material in a second process. The second process is carried out in a first processing chamber having at least a first radiant heat source positioned therein. A first predetermined amount of power is applied to the first radiant heat source prior to positioning the wafer in the first processing chamber so that the wafer reaches a first predetermined temperature in a first predetermined amount of time for carrying out the second process. The wafer is annealed in a third process. The third process is carried out in a second processing chamber having at least a second radiant heat source positioned therein. A second predetermined amount of power is applied to the second radiant source prior to positioning the wafer in the second processing chamber so that the wafer reaches a second predetermined temperature in a second predetermined amount of time for carrying out the third process. A dielectric layer is formed over the annealed layer in a fourth process. The fourth process is carried out in a third processing chamber having at least a third radiant heat source positioned therein. A third predetermined amount of power is applied to the third radiant source prior to positioning the wafer in the third processing chamber so that the wafer reaches a third predetermined temperature in a third predetermined amount of time for carrying out the fourth process. The wafer is transported between the processing chambers in a controlled ambient environment with the first, second and third processing chambers forming part of a cluster system.
Accordingly, it is an object of the present invention to provide a method for processing semiconductors. It is a further object of the present invention to provide such a method in which the processing temperature may be easily and readily controlled. It is another object of the present invention to provide such a method which may be used in a variety of different temperature and pressure environments. It is yet another object of the present invention to provide such a method in which production time is decreased and throughput increased. It is still a further object of the present invention to provide such a method which is relatively inexpensive and easy to perform. Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.